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The big and the small of the solar system

Fran Bagenal, Professor of Astrophysical and Planetary Sciences at the University of Colorado Boulder describes photos of Jupiter taken by the Juno spacecraft. Bagenal was a guest lecturer at the Green Bank Observatory last week. S. Stewart photo

Suzanne Stewart
Staff Writer

Last Wednesday at the Green Bank Observatory, Fran Bagenal, Professor of Astrophysical and Planetary Sciences at the University of Colorado Boulder, led a lecture titled, “Exploration of the Outer Solar System: New Horizons at Pluto and Juno at Jupiter,” in which she discussed the explorations to Pluto and Jupiter.

Bagenal was a member of both teams and worked with fellow scientists to launch spacecrafts to explore the smallest and largest planets in the solar system.

While there have been efforts to explore Pluto in the past – beginning with its discovery in 1930 by Clyde Tombaugh – it wasn’t until the New Horizons exploration when hi-definition photos were taken that they were finally able to deduce what Pluto is made of and what the surface looks like.

“This is the very best picture that Hubble ever took and you can see – look at the mountains and the valleys and the craters – no, you can’t see anything,” Bagenal joked, as she showed a blurry photo of Pluto. “No features at all. It has a sort of orangy tinge, but that’s all we knew.”

With the launch of New Horizons in January 2006, there was a collective nervous energy as the team awaited the returned data to see what Pluto had to offer.

“After nine-and-a-half years – this is our trajectory through the system – you’re moving at 33,000 miles an hour,” Bagenal said. “We go through this system in four hours. So, very quick flyby at that speed. This is tricky – the radio communication time between Earth and Pluto is four-and-a-half-hours so we could not joystick this spacecraft. We could say – go left, now go right, look over here, look over there. We had to program it and tell it what to do. Then it would send the data back. It’s a three kilobytes per second transmission. Very slow data rate. It took eighteen months to send all the data back.”

Once the data was received in 2015, Bagenal said many theories were confirmed and many discoveries made.

The team expected to see something akin to our moon, with impact craters, but it turned out that there are very few impact craters. What they saw were dips and valleys, holes and mountains.

“Very unexpected,” she said.

As expected, Pluto is part rock, part ice, but there are several types of ice – nitrogen ice, methane ice and possibly water ice. Those combinations create large scale mountain ranges and dense areas on the planet.

Bagenal also discussed the moons of Pluto – Charon, Hydra, Kerberos, Nix and Styx, and their unusual orbit around the planet.

From the smallest to the largest, Bagenal switched gears to talk about the current exploration of Jupiter – Juno.
Juno was outfitted to orbit Jupiter and collect data about the planet.

At 318 times the size of Earth, Jupiter holds many secrets about its interior, as well as its atmosphere.

“We want to go explore Jupiter to find out what it’s like inside and look for water,” Bagenal said. “These are the goals of our Juno mission – to find out where the water is, find out how much oxygen there is in the solar system. Jupiter is the biggest planet in the solar system, so we need to explain the water in Jupiter to get things right in our solar system formation theories.”

The Juno spacecraft is currently orbiting Jupiter, traveling around the poles and capturing data and hi-definition photos.

As it travels around the planet, the spacecraft is mapping the gravity field, magnetic field and aurora.

“The thing that’s dearest to my heart is the magnetic field and the charged particles that are trapped in the magnetic field of Jupiter,” Bagenal said. “We have a lot of particles that come from [moon] Io. Because this pesky moon Io has volcanoes, it ejects gasses, spews up sulfur, oxygen – it becomes ionized, trapped in the magnetic field, energized and eventually accelerates into the planet to form the aurora at the two poles.”

As with Pluto, the information Juno is sending back to the research team is giving a better picture of Jupiter, inside and out.

“The other thing we’ve been looking at is the gravity and measuring the gravity field,” Bagenal said. “What we’re finding is that there isn’t a distinct core that we thought would be there. There seems to be a mixing of this core material out a little further and the boundaries seem to be fuzzy.”

Bagenal joked that while she wasn’t thrilled about having a camera on the spacecraft – mainly because it took up too much data space – she was happy to see the resulting photographs.

“What about that camera – the one I was so sneering about – it took some amazing pictures,” she said. “What’s cool about it is that it’s a citizen’s science camera so you can go and vote on which objects you want to have taken. You can download the pictures almost immediately. You can go online and get them and you process them and upload them. You can talk about them and discuss them.”

After her presentation, Bagenal answered questions from the audience.

To learn more about the explorations, visit pluto.jhuapl.edu and mission juno.swri.edu

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